The present invention relates generally to phase change memory cells, and more specifically, to an in via formed phase change memory cell having a recessed pillar heater.
Phase change material has a variety of applications in microelectronic devices such as optical storage media and solid state phase change memory devices. Phase change random access memory (PRAM) devices, for example, store data using a phase change material, such as, for example, a chalcogenide alloy, that transforms into a crystalline state or an amorphous state during cooling after a heat treatment. Each state of the phase change material has different resistance characteristics. Specifically, the phase change material in the crystalline state has low resistance and the phase change material in the amorphous state has high resistance. The crystalline state is typically referred to as a “set state” having a logic level “0”, and the amorphous state is typically referred to as a “reset state” having a logic level “1”. A current passed through the phase change material creates ohmic heating and causes the phase change material to melt. Melting and gradually cooling down the phase change material allows time for the phase change material to form the crystalline state. Melting and abruptly cooling the phase change material quenches the phase change material into the amorphous state.
Over recent years, progress in lithographic and deposition techniques have provided new momentum towards the realization of practical phase change memory devices. However, for switching the device, a large current density across the phase change element is still needed, and effecting the switching of the memory cell utilizing currents and voltages compatible for integration into a feasible device remains a challenge as the device is scaled down. Thus, the cell switching dynamics would be greatly improved by decreasing the size of the switching volume. Current methods for fabricating a typical mushroom-type phase change memory cell include a reactive ion etching (RIE) process on the stack containing the phase change material to form the active part of the memory cell. Potential problems may arise such as diffusion of unwanted species or voids into the phase change material and/or internal or external interfaces during the RIE process or during subsequent deposition of dielectric layers.